A 25 percent by mass solution contains a solute of molar mass 50 g per mol and water as solvent. What is the approximate molality?
Answer and explanation
Correct answer: 6.67 mol kg^-1
Take 100 g of solution. It contains 25 g solute and 75 g water. Solute moles are 25/50 = 0.5 mol, while solvent mass is 0.075 kg. Therefore molality = moles of solute divided by kilograms of solvent = 0.5/0.075 = 6.67 mol kg^-1. The denominator is solvent mass, not total solution mass.
Frequently asked questions
What is the correct answer to this question?
6.67 mol kg^-1
Why is this the correct answer?
Take 100 g of solution. It contains 25 g solute and 75 g water. Solute moles are 25/50 = 0.5 mol, while solvent mass is 0.075 kg. Therefore molality = moles of solute divided by kilograms of solvent = 0.5/0.075 = 6.67 mol kg^-1. The denominator is solvent mass, not total solution mass.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Chapter 01: Solutions.
Student feedback
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
